Reverse lip blow molding

ABSTRACT

The present invention is directed to a blow molded article and an apparatus and method for blow molding the article. The article contemplated by the present invention includes a recessed lip. The apparatus includes two plates reciprocally movable toward and away from one another. A center ring member and a separating ring are fixedly and perpendicularly mounted on each plate. A mold half is mounted on each plate and is divided into two sections. One section is located on each side of the center ring member and is reciprocally movable toward and away from the center ring member. A first insert member is provided in each mold section in proximity to said center insert member. The first insert has a channel therein for receiving a second insert member. The second insert member is reciprocally movable in said channel and engages the center ring member. The movement of the second insert member is synchronized with respect to the first insert member to move at a speed that is at least half the speed of the first insert. The recessed lip is molded between said center ring members, the first insert member and the second insert member.

This is a division of application Ser. No. 07/717,736, filed Jun. 19,1991, now U.S. Pat. No. 5,364,675, which issued on Nov. 15, 1994, is adivision of application Ser. No. 07/462,178, filed Jan. 8, 1990, nowU.S. Pat. No. 5,051,084, which issued on Sep. 24, 1991, which is acontinuation-in-part of application Ser. No. 07/265,163, filed Oct. 31,1988, now U.S. Pat. No. 4,972,963, which issued on Nov. 27, 1990.

The subject matter of U.S. Pat. No. 4,972,963 is herein incorporated byreference.

FIELD OF THE INVENTION

The present invention is directed to blow molded plastic articles, andis specifically directed to an apparatus and method which forms a deeprecessed or reverse lip in a blow molded article.

BACKGROUND OF THE INVENTION

The term "recessed lip" or "reversed lip" as used herein refers to agenerally U-shaped hollow member which is formed at the upper open edgeof an article. The lip is provided to increase the rigidity andintegrity of the article.

The molding of a deep recessed lip into a plastic article hastraditionally been achieved through the use of injection molding. Blowmolding techniques have also been used to form a recessed lip in anarticle. Prior blow molding apparatus typically comprise twohorizontally reciprocally movable mold halves which are arrangedsymmetrically about a vertical plane. Each mold half is a mirror imageof the other. Each mold half may also be divided by a horizontal planeinto two vertically reciprocally movable sections. A mold of this typeis used to simultaneously form two articles which may be separated uponformation.

The blow molding process is initiated with all the mold parts separatedfrom one another. A parison or tube of plastic is extruded around a blowtube between the reciprocally movable mold halves. The parison istypically polyethylene, although any thermoplastic which is blowmoldable may be used. A polyethylene parison is typically extruded at atemperature of about 375° F. The mold halves are moved horizontallytoward one another. Pinch-off edges make a seal for the parison withinthe mold and prepare the flash for easy removal. The parison within themold is then inflated or pressurized with air between about 60 and 150psi. The parison is expanded into contact with the inner surface of themold cavity. A portion of the mold is formed radially outwardly of themold cavity that forms the main body of the article. The parison ispushed into the interior of the outward portions and forms the lip onthe article. Thereafter, the air pressure in the mold cavity may belowered to about 5 to 40 psi.

The mold cavity is also provided with sections that move verticallytoward one another so as to further define the lip. Such an apparatus isdescribed in copending application Ser. No. 07/265,163, now U.S. Pat.No. 4,972,963. As the mold sections are pushed together, the outwardlyextending portions of the lip are compressed. Further apparatus includemoveable mold sections that placed the outwardly extending portions intoan over lapping condition. Such an apparatus is described in U.S. Pat.No. 4,378,328.

The entire series of movements of the various mold sections occursrapidly, i.e., typically in less than two seconds. Once the internalpressure is withdrawn from the mold cavity, plates on the upper andlower portion of the molding apparatus retract away from the moldedarticle in a horizontal direction. The mold sections then move in avertical direction away from one another and the article is removed fromthe mold apparatus.

In some instances, the parison forming the lip buckles and thensolidifies. This causes undesirable stretching in certain areas of thelip and reduces the strength of the lip. The present invention providesthe capability for producing an article with a sturdy reverse lipwithout undesirable stretching, which lowers the mechanical strength andintegrity of the lip.

SUMMARY OF THE INVENTION

The present invention is directed to blow molding a deep recessed lip ina molded article. The lip as contemplated by the present inventionincludes a folded reinforcing layer adjacent a hollow U-shaped portion.The reinforcing layer is formed by the parison folding over on itself inthe mold while forming the U-shaped lip. The folded portions are pinchedtogether within the mold and are welded to one-another. At variousportions around the circumference of the lip, vents are inserted torelieve the pressure within the lip during release of the internalpressure within the molded article.

The present invention also contemplates an apparatus and method offorming a deep recessed lip in a blow molded article. The apparatusincludes a plurality of levers to synchronize the movement of the moldparts to form the lip and to form the reinforcing layer adjacent thelip. The synchronous movement of the mold parts results in betterdistribution of the parison in the lip area and prevents the parisonfrom bunching or wrinkling on the radially outer portion of the lip.

Another portion of the present invention includes structure for thesynchronous separation of the mold parts once the molding process iscomplete. The mold sections move simultaneously both vertically andhorizontally. The relative movement of the mold sections away from thelip area is controlled to maintain the integrity of the lip during theseparation. This relative movement, in conjunction with the simultaneousvertical and horizontal separation of the mold halves, results is afaster production rate and a reduction in the number of actuators neededto support the mold.

DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, there is shown in thedrawings a form which is presently preferred; it being understood,however, that this invention is not limited to the precise arrangementsand instrumentality shown.

FIG. 1 is an isometric view of a molded article made in accordance withthe present invention.

FIG. 2 is an isometric view of one half of the molded article shown inFIG. 1 having a deep recessed or reverse lip made in accordance with thepresent invention.

FIG. 3 is a partial cross section of the article as taken along lines3--3 in FIG. 2.

FIG. 4 is a partial cross section of a molding apparatus of the presentinvention.

FIG. 5 is a partial cross section of a second embodiment of a moldingapparatus of the present invention.

FIG. 6 is a cross section of a third embodiment of a molding apparatusof the present invention.

FIG. 7 is an isometric cross section of the molding apparatus shown inFIG. 6.

FIG. 8 is a second cross section of the molding apparatus shown in FIG.7.

FIG. 9 is a cross section of the molding apparatus of FIG. 8 taken alongline 8--8.

DESCRIPTION OF THE INVENTION

Referring now to the drawings, wherein like numerals indicate likeelements, there is shown in FIG. 1 an article 10 in accordance with thepresent invention. Article 10 is, for example, in the form of twocontainers 12 and 12' which are simultaneously molded during a singlemolding operation. The two containers 12 and 12' are joined togetheradjacent lips 14 and 14'. As illustrated in FIG. 2, article 10 isseparated, e.g., cut along a transverse plane substantially through itsmiddle, such that containers 12 and 12' are of equal dimension and thelips 14 and 14' form the periphery of the open upper end thereof.

The recessed lip 14 as contemplated by the present invention is shown incross-section in FIG. 3. Recessed lip 14 includes a generally U-shapedhollow member with an inner wall 18, an outer wall 16, and a curvedlower wall 20. An upper wall 22 is formed over the U-shape by a layer ofplastic folded inwardly toward the center of the container 12. The upperwall 22 is folded over the extension flange 23 between the body of thecontainer 12 and the U-shaped portion. The folding over of wall 22 andflange 23 serves to increase the mechanical strength of the lip 14 andcontainer 12. The lip 14 is provided with at least one vent 24 to allowpressurized air to escape from the hollow of the lip 14 and prevent thelip 14 from exploding after release of pressure within the mold duringthe molding process.

FIG. 4 illustrates a first embodiment of a molding apparatus 26 inaccordance with the present invention. Apparatus 26 comprises tworeciprocally movable mold halves 28 and 30. Left mold half 28 and rightmold half 30 are arranged symmetrically on opposite sides of verticalplane Y--Y. Mold half 28 is a mirror image of mold half 30. Each moldhalf 28 and 30 includes two vertically reciprocally movable sections.Mold half 28 comprises Sections I and III. Mold half 30 comprisesSections II and IV. Each mold half section is positioned on oppositesides of a center ring member 34 and 34', respectively. When the moldsections are closed (as illustrated, Sections III and IV), they definethe shape of article 10. Mold half 28 will be described in detail below.Those skilled in the art will understand that this description appliesequally well to mold half 30.

Mold half 28 includes a plate 32. Center ring member 34 is fixedperpendicular to plate 32 and perpendicular to plane Y--Y. Center ringmember 34 includes a separating member 36 which projects inwardly towardthe center of the molding apparatus 26. Plate 32 is moveablehorizontally. Sections I and III of mold 28 are slidably mounted onplate 32 via linear thrust bearings 38.

Mold Sections I and III include a movable plate 40 having a surface 40Athat rides on bearings 38. Plate 40 is capable of reciprocal movementtoward and away from ring 34. Mold wall 42 is rigidly fixed to plate 40along surface 40B. Plate 40 can be eliminated in which case mold wall 42would be slidably mounted directly on the bearings 38. Lower and upperpinch-off plates (not shown) are fixed to the upper and lower surface ofmold walls 42 of Sections I and III, respectively. The pinch-off platesare reciprocally movable perpendicular to the vertical Y--Y plane,toward and away from the center of the mold 26. The pinch-off platescooperate to form a cylindrical bore at the base of the mold andprovides clearance for flash from the parison and for the blow tube (notshown). The bottom pinch-off plates also include clearance on theirinner surfaces for excess plastic extruded during the molding process.When mold halves 28 and 30 are moved together, the pinch-off plates forma tight seal about the blow tube. Mold walls 42 and 42' and pinch-offplates together define a cavity 44 defined as two frusto-conical formswhich, when brought together, define the shape of article 10. Of course,if a different shape is desired, the shape of the cavity 44 willcorrespond to the desired shape.

A first insert member 46 is positioned within a recesses in the moldwall 42 proximal to center ring member 34. First insert member 46 formsthe upper end of container 12 adjacent lip 14. First insert member 46includes a channel 47 into which is placed a second insert member 48.First insert member 46 is preferably made of steel, but any metal withthe properties similar to those of steel will suffice. Second insertmember 48 is reciprocally movable within the channel 47 in the Y--Ydirection. The first insert member 46 and is biased away from theinterior of the channel 47 by coil springs 50 (only one spring 50 beingshown for each mold section). Second insert member 48 is preferably madeof bronze, but any metal having properties similar to those of bronze inrelation to the materials of the first insert member 46 will suffice.Second insert member 48 is L-shaped in cross-section and is reciprocallyslidable between a first position (Section I) and a second position(Section III). The L-shape forms a shoulder 52. Springs 50 bias secondinsert member 48 to the first position, i.e., out of the channel in ringmember 46 when the mold is separated. Springs 50 maintain second insertmember 48 in its projected position until the movement of the moldsections causes engagement of shoulder 52 with ring member 34.

Parison 54 when pressurized within the mold cavity 44 engages theprojected concave surface 48B of second insert 48. Thereafter, firstinsert 46 and second insert 48 initiate their movement toward the centerring member 34. Upon engagement of the shoulder 52 of second insert 48with ring member 34, the first insert 46 continues to move toward ringmember 34 and separating member 36. This relative movement of the moldsections causes the parison 54 to form the hollow U-shaped lip 14 (seeSection III). The relative spacing between the projection of separatingmember 36 and the vertical projection of first insert 46 is controlledto permit the overlap of flange 23 and upper wall 22 by the lip 14. Thisrelationship is illustrated in Sections II and IV. Preferably these twoportions weld together and seal the hollow of the U-shape. Asillustrated by Section I and III, the vertical projection of firstinsert member may be reduced so as to provide a gap between theformation of the upper wall 22 and the flange 23. This gap forms thevent 24 in the lip 14 area for release of pressure within the lip hollowduring release of pressure in the mold cavity 44. During the separationof the parts of apparatus 26, the relative movement thereof is oppositethat in forming the article 10.

FIG. 5 illustrates a second embodiment of the molding apparatus 26' ascontemplated by the present invention. In FIG. 5, only Sections I andIII of mold part 28 have been illustrated. The apparatus 26' shown inthis FIG. 5 includes a lever mechanism 58 to synchronize to formation ofthe lip 14. One end of lever 58 is fixed to the first insert member 46at pivot 59. The opposite end of lever 58 is connected to push rod 60 atpivot 66. Push rod 60 as shown is attached by screw threads to centerring member 34. However, due to the force of spring 64, the push rod 60need only contact center ring 34 for proper synchronization of themovement of inserts 46 and 48. Along the length of the lever 58 is acontact projection 61. Contact projection 61 rids on flange 62. Flange62 projects from a shaft 63 which is fixed at one end to second insertmember 48. The opposite end of shaft 63 is mounted in mold wall 42.Shaft 63 is biased toward center ring 34 by spring 64 such that theflange 62 normally engages projection 61 on lever 58.

In the operation of this second embodiment 26', the vertical movement ofthe mold parts 40 and 42 toward the center ring member 34 causes arelative movement between the first insert member 46 and second insert48. The relative speed of these parts is determined by the position ofthe projection 61 between pivots 59 and 66. As will be discussed furtherbelow, the placement of the projection 61, and its corresponding contactwith flange 62, is preferably at a distance from pivot 59 that is lessthan one half of the length of the lever 58. Thus, first insert 46 willmove toward ring member 34 at a speed less than twice that of the secondinsert member 48. However, both members reach center ring member 34 atsubstantially the same time.

Illustrated in FIGS. 6 and 7 is another alternate embodiment of amolding apparatus 26". This third embodiment includes a synchronizedmovement of the mold parts that is similar to that accomplished byapparatus 26' in FIG. 5. In this alternate embodiment, one end of lever68 contacts wear plate 70 on mold part 42. The opposite end of lever 68contacts flange 82. Flange 82 is formed at one end of shaft 83. Theopposite end of shaft 83 is fixed to center ring 34. Lever 68 is pivotedto second insert member 48 at pivot 84. The placement of pivot 84 isdetermined by the desired relative speed of the first insert 46 ascompared to the second insert 48. Since the speed of second insert 48 isdesired to be greater than one half the speed of first insert 46, thepivot should preferably be located no greater than one half the lengthof the lever 68 from the end thereof contacting wear plate 70 on moldpart 42.

The synchronous movement of first insert 46 and second insert 48, ascontemplated by the embodiments of the molding apparatus shown in FIG. 5and FIGS. 6 and 7, controls the flow of the parison 54 in the formationof the lip portion 14 of container 12. The relative movement of the moldparts allows the parison 54 to be rolled around the concave surface 48Bon second insert 48. Control of this relative speed results in an evendistribution of the parison 54 in the lip 14, particularly in the areaof inner wall 18.

In the embodiment of molding apparatus 26 shown in FIG. 4, the innerwall 18 of lip 14 may become somewhat elongated, and thus thinner, ascompared to the other portions 16, 20, and 22 of the lip 14. Thisthinned area is caused by a stretching of the inner wall 18 area due tothe relative progression of first insert 46 as compared to second insert48. In the alternate embodiments 26' and 26", the relative speed of theinserts 46 and 48 cause the compression of the outer wall 16 withoutbunching and without the inner wall 18 becoming stretched. The arrivalof the parts 46 and 48 into the desired position to form lip 14 issubstantially simultaneous due to the relative speed of insert 48 beinggreater than one half of the speed of insert 46. This relative movementresults in a lip 14 which is substantially uniform in formation andwhich does not include weakened areas resulting from wrinkled orimproperly hardened plastic. For these reasons, these alternateembodiments 26' and 26" are preferred.

FIGS. 8 and 9 illustrate means for releasing the molding apparatus 26"once the article 10 has been molded. In this embodiment, when theparison 54 is cooled, plates 32 and 40, mold wall 42, and center member34 move in a horizontal direction away from the cavity 44. At the sametime, mold wall 42 moves in a vertical direction away from center member34. When the mold is closed, the shoulder 52 of second insert member 48in this embodiment is in direct contact with center member 34. Also, theprojection of first insert member 46 must clear the lower wall 20 of thelip 14 prior to its horizontal movement. For this purpose, a spring bolt74 is placed in a channel 75 which extends through second insert 48 andterminates within first insert 46. A spring 76 is placed in channel 75.Spring 76 extends between plate 40 and an internal limit stop 72 withinfirst insert member 46. The opposite end of spring bolt 74 includes abolt head 74B which is retained within passageway 78 in insert 46.Passageway 78 provides for limited movement of the bolt head 74B uponhorizontal movement of the plate 40. Thus, as mold parts 34, 40 and 42move horizontally, the compressed spring 76 keeps first members 46 frommoving in the horizontal direction until bolt head 74B reaches theinternal limit of passageway 78. However, insert portions 46 and 48 ofthe mold are free to move vertically with the mold wall 42. When bolthead 74B reaches the end of passageway 78, inserts 46 and 48 movehorizontally with parts 40 and 42. This occurs after the projections ofinserts 46 and 48 have cleared the lip 14. This relationship of the moldpart movement permits the reduction in the number of actuators requiredfor mold separation and increases the number of cycles that theapparatus 26" may perform in a given amount of time.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential attributes thereof and,accordingly, reference should be made to the appended claims, ratherthan to the foregoing specification, as indicating the scope of theinvention.

We claim:
 1. An article made using a blow molding process comprising: asubstantially circular side wall; a closed bottom end; an open top end;and a projecting lip positioned on the outer circumference of the opentop end, the lip including a web portion extending outwardly from theperiphery of the open top end, a recessed portion attached to said webportion and having a substantially U-shaped cross-section, the recessedportion being radially separated from the side wall by the web portion,and a layer of material extending from and folded inwardly over theU-shaped portion and extending adjacent to the web portion.
 2. Anarticle made using a blow molding process comprising:a substantiallycylindrical body having a substantially closed bottom at one end and anopen top at the opposite end; and a lip formed on and encircling atleast a portion of the top end, the lip including a web portionextending outwardly from the body and including a recessed portionhaving an outer wall, an inner wall and a lower wall connecting theouter wall to the inner wall so as to form a cavity therebetween, and anupper wall attached to the outer wall and extending inwardly toward thebody, the upper wall being parallel to and overlying the web portion,wherein the recessed portion is radially separated from the cylindricalbody by the web portion.
 3. An article according to claim 2 furthercomprising at least one vent opening in said recessed portioncommunicating with the cavity.
 4. An article according to claim 3wherein said at least one vent opening is between said web portion andsaid upper wall.
 5. An article according to claim 2 wherein said upperwall is attached to said web portion at least at one location.
 6. Anarticle according to claim 2 wherein a portion of said upper wall isattached to said web portion.
 7. An article made using a blow moldingprocess comprising:a substantially cylindrical body having asubstantially closed bottom at one end and an open top at the oppositeend; a reinforcing lip formed on and encircling the top end, the lipincluding a web portion extending outwardly from the body and includinga recessed portion having a substantially U-shaped cross-section, therecessed portion being radially separated from the cylindrical body bythe web portion, and an upper wall attached to and folded inwardly overthe recessed portion, said upper wall extending inwardly toward the bodyand attached to said web portion at least at one location; and at leastone vent opening in said recessed portion between said web portion andsaid upper wall.
 8. An article made using a blow molding processcomprising:a substantially cylindrical body having a generally closedbottom at one end and an open top at the opposite end; and a lip formedon and encircling the top end, the lip including a web portion extendingoutwardly from and integrally formed with the body, a recessed portionintegrally formed with the web portion, the recessed portion having anintegrally formed outer wall, inner wall and lower wall, the inner wallextending between the outer wall and the inner wall so as to form acavity therebetween, the recessed portion being radially separated fromthe cylindrical body by file web portion, and an upper wall integrallyformed with the outer wall and extending inwardly from the outer walltoward the body, the upper wall overlying and attached to the webportion.
 9. An article according to claim 8 further comprising anintegral vertical ridge extending upwardly at the open top end of thebody, the ridge integrally formed with the upper wall and attached tosaid web portion.
 10. An article made using a blow molding processcomprising:a substantially frusto-conical body having a generally closedbottom end and an open top end; a lip formed adjacent to and encirclingat least a portion of the open top end, the lip including a web portionextending outwardly from and integral with the body, a recessed portionradially spaced from the body and integrally formed with the webportion, the recessed portion having spaced outer and inner wallsintegrally formed with one another, an upper wall integrally formed withouter wall, the upper wall extending inwardly toward the body from theouter wall and defining a cavity along with the outer and inner walls,the upper wall overlying and bonded to the web portion.
 11. An articlemade using a blow molding process comprising:first and secondsubstantially frusto-conical portions axially aligned with one another,each frusto-conical portion having a generally closed end and a radiallip, the lip encircling the respective frusto-conical portion at alocation spaced from the corresponding closed end, each lip including aweb portion extending outwardly from and integrally formed with thefrusto-conical portion and a recessed portion integrally formed with theweb portion, the recessed portion having an integral outer wall andinner wall with a cavity defined therebetween, the recessed portionbeing radially separated from the frusto-conical portion by the webportion, an upper wall integrally formed with the outer wall andextending inwardly toward the frusto-conical portion, the upper walloverlying and bonded to the web portion, and a cylindrical flangeextending bet-ween and formed integrally with the respective radial lipsof the first and second frusto-conical portions